Optimization of welding processes requires attention to several parameters simultaneously. In many situations, these parameters include both spatial and thermal relationships between weld process materials and weld process ancillary apparatus or equipment. The weld process materials may include strip or other stock materials, tubing, welding rods, or other materials used in the welding process, and the weld process ancillary apparatus or equipment may include weld-roll boxes, impeders, mandrels, coolant lines, material handling, tooling, robotic arm assemblies for handling weld process materials or equipment, welding heat sources such as induction coils and electrical contact tips, welder unit, power supply unit, and other process ancillary apparatus or equipment.
One type of welding process is known as electric resistance welding (ERW), which can be used to weld the seam of tubular articles or products such as tubes and pipes from strip stock. The ERW process can also be used to weld engineered structural sections or products such as I-beams, and T-beams. The ERW process for tubular products involves the introduction of an electrical current at strip edges via induction or directly applied electrodes. The supplied current heats up the strip edges, which are then forged together when passed through a weld box.
FIG. 1(a) and FIG. 1(b) illustrate one example of ERW where tube 113 is formed from a metal strip forced together at weld point 115 to form weld seam 117 as the strip advances in the direction of the single headed arrow and pressure force is applied in the directions indicated by the double headed arrows to force the edge portions of the strip together. In FIG. 1(a) induction power can be supplied from a suitable ac power source (not shown in the figure) to induction coil 121 to induce current in the metal around a “V” (vee) shaped region formed by forcing edges of the strip together. The induced alternating current flows around the outside of the tube and then along the open vee-shaped edges to weld point 115 as illustrated by the typical flux line 119 (shown as dashed line) in FIG. 1(a). The length, 23, of this “V” shaped region can have a maximum value equal to the distance between the end of the coil closest to the weld point and the weld point.
FIG. 2 illustrates one example of an ERW process similar to the process in FIG. 1(a) and FIG. 1(b) except that induction coil 121 is replaced by a pair of contacts (electrodes) 8 and 9 as the supply of heat that in this example are connected to an electric current source which may be alternating current, or direct current, in other examples. FIG. 2 illustrates forge welding together at a weld point 1 a pair of edge surfaces 2 and 3 which can be the edge surfaces of a pair of metal strips 10 and 11 or the opposite edge surfaces of a single metal strip which has been deformed to form a tube as in the FIG. 1 process. The edge surfaces 2 and 3 are advanced in the direction of the arrow 4 and are separated by a gap 5 in advance of the weld point 1. In some processes, to take advantage of the “proximity effect,” the gap is relatively small, and the angle 6 between the edge surfaces can be about 2 to 7 degrees, or other angles as deemed appropriate for the process. A weld seam 7 is present following the weld point 1. In this example high frequency electric current, e.g. current of a frequency of at least 10 kHz, is supplied to the edge surfaces 2 and 3 by way of a pair of contacts 8 and 9 in sliding engagement with the top surfaces 10 and 11 of the part or parts with one contact 8 at one side of the gap 5 and the other contact 9 at the other side of the gap 5. The contact 8 is adjacent to the edge surface 2, and the contact 9 is adjacent to the edge surface 3. Normally, there is a small spacing between the edge surfaces and the respective contact as shown. From the contacts 8 and 9, the high frequency current flows in the part or parts along a plurality of contiguous paths to the edge surfaces 2 and 3, only three of the paths for each contact, paths 16-17-18 and 19-20-21, being indicated in dotted lines in FIG. 2. With direct current or low frequency current, the amounts of current in each path is determined only by the resistance of each path, and therefore, the current in each path does not vary significantly. However, with high frequency current, the magnitude of current in each path is determined not only by the resistance of each path which, due to skin effect, is higher than the direct current resistance, but also by the reactance of each path.
It is one object of the present invention to provide a heat energy sensing and processing system and method for a weld region in a welding process that can include an electric resistance welding process, including electric resistance welding processes where a stock strip is welded into a tubular product, or a fusion welding process.